This invention relates to methods for dispensing rolled fabric on a building structure. More particularly, this invention relates to methods for dispensing a rolled fabric across the width of at least two longitudinal structural supports (e.g. purlins or girts) of a metal building structure.
Metal roof structures are typically comprised of a series of rafters which extend parallel to each other from one side of a building to another. Longitudinal structural supports (referred to as girts, purlins or bar joists, herein used interchangeably) are typically mounted on top of and perpendicular to these rafters in a similarly parallel fashion. In like fashion, the walls of a building may be comprised of a series of vertical studs or columns on which the aforesaid girts are mounted in a horizontal fashion (perpendicular to the studs or columns).
In one known manner of fabricating such conventional metal roof and wall structures, a rolled fabric (e.g. polyethylene) is first rolled out in sheet form over the structural supports before installing the fiberglass insulation batting in order to serve as a vapor barrier (a.k.a. xe2x80x9cretarderxe2x80x9d) for the roof or wall system. The sheets are usually placed in an overlapping edge arrangement so as to be sure to form a continuous vapor barrier. Insulation usually in the form of rolled out fiberglass insulation batting is then installed over the sheet(s) of fabric. The insulation is secured in place by placing over it hard (typically metal) sheeting called roof sheeting. These hard sheets are then attached with roofing (or wall) panel fasteners (screws, for example) which ultimately hold the fabric and insulation in place against the upper surface of the flange of the purlins.
Heretofore, it has been known in the art to install such rolled fabric across the top of purlins by hand or by various carriage devices, in a substantially taut manner, such as described in U.S. Pat. Nos. 4,635,423 and 4,736,552. Utilizing such a taut sheet when building an insulated roof or wall structure gave rise to a drawback in prior art systems which inherently reduced the R-value of the insulation in the final roof system. For example, in certain conventional installation techniques heretofore used in the art, when the metal sheeting was attached to the upper surface of the purlins and the metal sheeting secured, the sheeting compressed the insulation between this sheeting and the sheet of fabric which has been pulled tight and secured by the sheeting fasteners. Thus, the insulation, normally a fiberglass batt of a specified thickness to achieve the required R-value, could not recover to its original thickness, resulting in a loss of R-value, often significantly below its intended value.
One known system which attempts to overcome this compression problem is disclosed in U.S. Pat. No. 5,653,081. In this system, a pleat system is pre-manufactured into a sheet of rolled fabric. When the fabric is the installed (unrolled) parallel, but overlapping the purlins, the pleats unfold into the insulation cavity, which may be defined as the volume or space between any two adjacent purlins and the depth of the pleat. When an elongated batt of insulation is laid parallel to the purlins, the batt if appropriately made to have a width equal to that of the space between the two adjacent purlins, is able to occupy the insulation cavity created by the unfolding of the pleats. In theory, by selecting an appropriate combination of pleat number and size which corresponds to each given R-value (as governed by the thickness of the insulation batt), a depth of draped cavity may be achieved in the fabric which overcomes the compression problem. Ideally, a pleat number and size will be manufactured into the fabric sufficient to create a draped cavity of depth xe2x80x9cxxe2x80x9d or slightly more, which will then match a batt of thickness xe2x80x9cxxe2x80x9d corresponding to a desired R-value. Opposing pleats which form an insulation cavity, must also, of course, be manufactured to a spaced distance similar to the spacing between purlins . . . spacing which may vary from building type to building type.
In such a system, therefore, the desired number and size of pleats necessary to achieve a depth of draped insulation cavity corresponding to any given R-value must be pre-manufactured at significant expense into a fabric itself for each R-value and purlin width anticipated for use. The use of different R-values is prevalent in commerce, and as stated aforesaid, purlin spacing is not always a standard distance. Not only does this then create inventory problems, but, of course, it is also not possible to select an insulation thickness or R-value on site once a particular roll of sheeting is delivered without having to delay construction until rolls of fabric having the requisite pleat dimensions are delivered. Moreover, if too small a pleat size is delivered to the job site or inadvertently (or knowingly, to save time) loaded on a dispensing device and installed as part of the roof system, a significant reduction in the agreed to R-value may well occur.
In view of the above, it is apparent that there exists a need in the art for a rolled fabric dispensing method which overcomes the above drawbacks. It is a purpose of this invention to fulfill this need in the art, as well as other needs which will become apparent to the skilled artisan once given the following disclosure.
Generally speaking, this invention fulfills the above-described needs in the art by providing in the method of constructing an insulated roof or wall system which includes a pair of spaced, substantially parallel structural members comprised of a longitudinal surface for receiving thereon a sheet of vapor barrier material, the steps comprising applying a sheet of vapor barrier material across said pair of structural members, applying a layer of compressible and recoverable insulation having a predetermined thickness which at least in part determines the R-value of the insulation over the sheet of vapor barrier material, and applying a cover material overlying the layer of insulation, the improvement comprising the steps of:
a) overlaying the longitudinal surfaces of the pair of opposing structural members with an untaut sheet of vapor barrier material having an untaut width sufficient to allow the formation therewith of an insulation cavity between the pair of structural members to a depth of drape sufficient such that when the insulation layer resides in the cavity, a portion of the insulation has a thickness approximately equal to the said predetermined thickness;
b) overlaying the untaut sheet of vapor barrier material with a layer of said insulation;
c) forming the insulation cavity to said depth of drape wherein a substantial portion of the insulation is located in the cavity;
d) overlaying the insulation with a covering material; and
f) forming a structurally integrated roof or wall system by securing the vapor barrier sheet, the insulation and the covering material to each other and to the structural members,
whereby a substantial portion of said insulation in said cavity has a thickness approximately equal to said predetermined thickness.
In one embodiment of this invention a single roll of vapor barrier fabric extends across the entire span of the roof or wall being covered. In other embodiments, multiple, adjacent short rolls of the fabric are used to create an overlapping sheet arrangement which spans the surface of the wall or roof in a staggered array so that excess fabric does not extend into the building. In such an embodiment the method includes unrolling a first leading roll of fabric a given distance, unrolling a second roll of fabric located adjacent the first roll a distance which is less than the distance traveled by the first roll thereby to create a trailing roll of the second roll with respect to the first roll.